1. Field of the Invention
This invention relates to an implantable medical device, and more particularly, to a prosthesis assembly for the remedy of impotence.
2. Description of the Prior Art
Inflatable or distensible penile implants have been used for treatment of impotence. An early patent on an implant system for this purpose is U.S. Pat. No. 4,009,711, issued to Uson, et al., which discloses a pair of inflatable tubes to be surgically implanted in a corpus cavernosum of the penis. Each of the tubes includes a non-distensible portion of a semi-rigid material to be implanted into the root end of the corpus cavernosum and a pendulous, distensible body portion. The distensible or inflatable body or tube is connected by tubing to a fluid reservoir located in the scrotal sac, and a check valve is provided to control the flow of fluid between the reservoir and inflatable tube. A similar device is disclosed in U.S. Pat. No. 4,235,227, issued to Yamanaka.
A more recent patent on the prosthesis is U.S. Pat. No. 4,726,360, which discloses that each extendable tube can be encased in an outer sleeve which is permanently filled with a fluid, thereby providing an outer, annular pressure chamber.
The distensible tubes in the implants, which have heretofore been used, are formed of silicone and have limited elasticity to avoid girth expansion of the tubes. The limited elasticity of the tubes, however, undesirably limits their axial extendability.
U.S. Pat. No. 4,730,607, issued to Fischell discloses that the axial extendibility of a stiffener cylinder can be improved by providing several bellow-type folds in the tube. The bellow folds are described as having sufficient depth to increase the extendibility of the tube from 6 percent to about 13 percent. Fischell teaches that these folds should preferably be located near the base to function as a strain relief. However, the extendibility is unsatisfactorily limited if the stiffener cylinder is supplied with an outer sheath.
Despite the various attempts to provide a satisfactory penile implant, none of the prior art approaches has provided a corpus cavernosum implant which is extendable for a significant percentage of its length without an objectionable increase in girth. In such structure it is important to minimize the pressure or stress points of the tube under inflation to avoid premature failure.
While the bellows configuration of an inflatable tube is an apparent solution to the necessity for optimum elongation of the tube, this structure has not found acceptance in practice, presumably because of the sharp folds and edges of a bellows construction which localizes stress at the folds, thus limiting the practicality of this approach. This approach also has some aesthetic disadvantages in tactile sensing of the irregular shape.